Over 2×1011 metric tons of lignocellulosic material is produced by natural source annually. As feedstock, this material would provide theoretical energy of 3×1018 kJ, which corresponds to ten times annual energy consumption of the entire world. In order to tap such energy resources, key technology must be developed, namely, that of improved production of green sugars for subsequent generation of green fuel and chemicals by biological conversion. Cellulosic ethanol became a reality in 2015, when several corn ethanol plants developed new “bolt-on” processes with multiple, onsite production lines for producing fuel and chemicals. (RFA, Fueling a high octane future. 2016, Renewable Fuels Association) Commercial cellulose-based sugar production was a turning point from process scale up and demonstration. However, lignocellulosic pretreatment, either by thermal or chemical means, is necessary to convert biomass so that it is accessible for enzymatic action. Unfortunately, current processes are complex and require high capital expenditure (CAPEX) and operational expenditures (OPEX). The need for a simple, economical conversion method is urgent.
Existing processes typically use homogenous acids, such as H2SO4 or HCl, and biological enzymes to convert lignocellulose into green sugars. However, these tools are burdened by many technical and economic problems.
There is a need to develop processes that will dramatically reduce the processing cost and time for converting lignocellulosic into fermentable sugars, thus providing an effective feedstock for biofuels and bio-based chemicals. Solid acid catalysts provide certain advantages and may permit cost of biofuel to reduce below that of petroleum-derived gasoline once implemented by biofuel producers based on lignocellulosic feedstock.
Several solid catalysts are known, such as acid resins, metal oxides, and zeolites, that fractionate cellulose into sugars and various oligomers. (Li et al., 2016; Hu et al., 2016; Rinaldo et al., 2010; Schneider et al., 2016) However, despite their potential, there is a dilemma with using solid acid catalysts. Specifically, solid acid catalysts have a problem of low substrate load (Schneider et al., 2016; Verma et al., 2014; Shuai et al., 2012), poor reaction mediums or low yields of specific mono sugars. (Hu et al., 2016; Rinaldi et al., 2010; Onda et al., 2008; Zhang et al., 2014) To date, typical cellulose loading has been limited to less than 15%. Additionally, some solid catalysts have a problem of low or no yield of mono sugars, for example, core-shell Fe3O4@ SiO2—SO3H acid catalyst reports high turnover of reducing sugars but no report of mono sugar hydrolysis.
Thus, there is a need for an improved method which more efficiently fractionates lignocellulosic material into green sugars and high value chemicals. The present disclosure describes a solution which solid phase catalyst that incorporates a transition metal complex and magnetic properties that can dramatically reduce the processing cost and time to create fermentable sugars from lignocellulosic biomass to produce biofuels and bio-based chemicals. The inventive catalysts can function under high cellulose load and have low catalyst loading requirements, while also producing monosaccharides.
Thus, there is a need for an improved method which more efficiently fractionates lignocellulosic material into green sugars and high value chemicals. The present disclosure describes a solution that dramatically reduces the processing cost and time to create fermentable sugars from lignocellulosic biomass, thus providing a green and economical feedstock for biofuel and bio-based chemical production.